Many functions of modern devices in automotive, consumer and industrial applications, such as converting electrical energy and driving an electric motor or an electric machine, rely on semiconductor devices such as such as Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) and Insulated Gate Bipolar Transistors (IGBTs).
In an IGBT, an isolated gate FET (Field Effect Transistor) is used for control of a bipolar transistor. In so doing, the low on-resistance Ron and the fast voltage control of the isolated gate FET is combined in a single semiconductor device with the high current and low saturation voltage (VCEsat) of the bipolar transistor. Accordingly, IGBTs are widely used in medium to high-power applications such as switching mode power supplies, inverters and traction motor controls. A single power IGBT may have a current switching capability of up to about 100 A or more and may withstand blocking voltages of up to 6 kV or even more.
Typically, a high ruggedness against latch-up, i.e. against a failure mode in which the IGBT can no longer be turned off by the isolated gate, is often desired. Depending on design, even a small defect density during manufacturing may result in lowering the ruggedness against latch-up of the manufactured IGBTs.
Accordingly, there is a need to improve manufacturing of bipolar semiconductor devices.